JP 2008-81690984 discloses a contact-force measuring device for a voltage drop type pantograph. The device measures the voltage from a pantograph so as to measure the pantograph contact force from the changes in the voltage. The system comprises a high pass filter or a frequency analyzer connected to a measuring instrument.
Further, according to the European standard EN 50317-2012 a monitoring system should take into account that all couples of sequential detachment with a return time<=1 s are considered as a unique detachment and a single detachment with time duration below 5 ms are not taken into account. Further, according to the standard the time duration of each arc generation, the train speed during the test, the number of arc, the sum of the duration of all arcs, the duration of the longest arc, the total operative time of the controlled section and the percentage of arcs should be determined.